KANSAS CITY, Mo. (AP) – The police chief in Kansas City, Missouri is defending his officers’ use of pepper spray in handling protesters outside of Republican presidential hopeful Donald Trump’s rally Saturday night.

Chief Darryl Forte says in a series of tweets and on his blog that the protesters included a “heavy presence of known anarchists” outside The Midland in downtown Kansas City. That’s where Trump staged a rally that was repeatedly interrupted by protesters inside.

Forte says the event attracted a bomb threat and “outside agitators,” and on his blog he says pepper spray was deployed only after a crowd ignored several minutes of orders to clear the street. Forte also said tensions had mounted, including one moment when two groups numbering about 200 people prepared to fight.

Forte says four people were arrested.